1. Field of the Invention
The present invention relates to environmentally stable organic polymers and, more particularly, to processible polymers synthesized from N-alkylsubstitued carbazole and p-acetoxybenzaldehyde which are highly conducting as synthesized. The term polymer as used herein also includes oligomers where indicated.
2. Related Art
Organic materials that behave as metals or semiconductors provide the advantages of these materials together with additional advantages of being soluble in organic solvents or having low melting points and glass transition temperatures. This minimizes the cost of processing and permits composites to be made with thermally sensitive materials such as doped Si or GaAs, for example. The enormous molecular design flexibility of organic chemistry enables precise tailoring of properties to fill a wide range of applications as enumerated above. In addition, the high strength and conductivity-to-weight ratios lend the advantage of fabrication of many electrical devices of much lower weight than conventional materials.
Theoretically, conductivity takes place both along the polymer chain and between adjacent chains. The active charge carrier, at least in the aromatic materials, is believed to be a bipolaron that is delocalized over several polymer repeating units. The mobility of such a species along the polymer chain is reduced by conformational disorder, necessitating a rigid highly crystalline chain structure for maximum intrachain conductivity. Various mechanisms such as "hopping" and "interchain exchange" are thought to be responsible for the interchain part of the conductivity. Unfortunately, all of the most highly crystalline polymers of high conductivity are insoluble and infusible. Therefore other materials have been sought.
Successful environmentally stable doped conducting polymers are described in U.S. Pat. No. 4,452,725 to S. T. Wellinghoff, S. A. Jenekhe (an inventor in the present application) and T. J. Kedrowski and has a common assignee with the present application. That patent concerns conducting polymers of N-alkyl 3,6' carbazolyl chemically doped with charge transfer acceptor dopants such as halogens. Environmentally stable polymer complexes of processible poly (3,6-N-alkylcarbazolyl alkenes) which also become highly conductive upon doping with charge transfer acceptors such as iodine are described in U.S. Pat. Nos. 4,548,738 and 4,598,139 also to the same S. A. Jenekhe and one B. J. Fure and commonly assigned with the present application. Organic polymers synthesized from carbazole or N-substituted carbazoles and benzaldehyde or certain substituted benzaldehydes also made conductive by virtue of doping with charge transfer acceptors are disclosed in yet another commonly assigned S. A. Jenekhe invention in U.S. Pat. No. 4,624,999.